The present invention relates to metal working lubricants and, in particular, to water base metal working lubricants. Lubricants are employed in metal working operations such as cutting, rolling, drawing and milling in order to reduce friction and heat and thereby wear and tear on the metal working tools and in general to facilitate the metal working operation.
The use of lubricants is, of course, a standard expedient in the art and both petroleum oil base and water base lubricants are well known. Generally, oil base lubricants provide excellent lubricity but have a tendency to form undesirable deposits and excessive smoke at high temperatures. Water base lubricants do not have these disadvantages and, because of the high specific heat of water, display generally superior cooling ability. Water base lubricants do have a tendency to cause rusting or corrosion of the tools and metal. However, suitable anticorrosive additives can control the corrosion problem and water base systems find wide employment because of the above-mentioned advantages.
There are two general types of water base metal working lubricants. The soluble type uses ingredient additives which are soluble in the water base to form a true solution. The emulsion type contains water emulsifiable ingredients which are emulsified in the water base by emulsifiers and remain suspended in the water as minute droplets. There are certain characteristics of each of these two types of water base lubricants. Performance of water soluble lubricants tends to fall off at a fairly uniform rate as the concentration of the effective ingredients diminishes with repeated use of the lubricant so that performance corresponds rather closely to the concentration of the soluble ingredients remaining in solution. On the other hand, emulsion type water base lubricants tend to maintain fairly uniform performance characteristics over rather protracted periods of use until the dilution factor becomes so great as to interfere with their effectiveness. At this point, performance falls off rather abruptly.
Thus, the emulsion type water base lubricant has the advantage of generally uniform performance characteristics throughout most of its useful life but has the disadvantage of requiring that care be taken to maintain the active ingredients in emulsion. Both water base types usually require additives to control the formation of bacteria in the lubricant during storage or use and to control the corrosive effects of water on many of the metals on which the lubricant is used.
Numerous different formulations for water base metal working lubricants are, of course, known. For example, U.S. Pat. No. 3,813,337 discloses a metal working lubricant which includes a lubricating oil, a noncationic emulsifier, an overbased alkali metal or alkaline earth metal sulfonate, a chlorinated hydrocarbon component and a coupling agent in a stabilizing amount of water. The composition is combined with a major amount of water to form an aqueous emulsion.
U.S. Pat. No. 3,933,660 discloses a reducing hot rolling oil for copper and copper alloys comprising a major quantity of water, at least one member selected from carboxylic acid type, sulfate type and phosphate type anionic surface active agents, and at least one other member being a hydroxyl group containing compound selected from alcohols, alkylene glycols and glycol ethers.
It is an object of the present invention to provide a novel water base metal working lubricant which is highly efficacious in use and which combines both a water soluble component and a water emulsifiable component.
It is another object of the present invention to provide a novel metal working composition which provides a water base lubricant including a water soluble component having a reverse solubility curve, an emulsifiable high pressure lubricating component and an emulsifier for the latter.
It is another object of the present invention to provide a water base metal working lubricant which displays the stability characteristics typical of water soluble type lubricants and the uniform performance characteristics typical of the emulsion type lubricants in a lubricant of superior performance characteristics. Other objects and advantages of the present invention will be apparent from the following description thereof.